Catalytic performance of invertase immobilized by adsorption on anionic exchange resin

Invertase (E.C.3.2.1.26; Km = 17.0 mM, Vmax = 0.0240 U mL−1, optimal activity at 55 °C and pH 5.0) was adsorbed on DOWEX®-anionic resin (types 1X2:100-400, 1X4:50-400 and 1X8:50-400), resulting in the DOWEX®-1X4-200 as the best support. One hundred milligrams of DOWEX®-1X4-200 were suspended in a 25 mL invertase solution (total activity 35 U) at 32 °C, pH 5.5, agitation of a 100 rpm for 4 h. The complex DOWEX®-1X4-200/invertase (D1X4-200I) (Vmax = 0.0450 U mL−1 and Km = 18.3 mM) had an optimal activity at 45 °C and pH 4.5. The catalytic performance of D1X4-200I was evaluated through the sucrose hydrolysis in a continuous membrane reactor coupled with a UF-membrane (cut off 100 kDa) or a MF-membrane (a pore diameter of 5 μm). The assays were carried out for at least 30 h under an agitation of 100 rpm, a dilution rate of 1.6 h−1, a substrate concentration of 2.5 mM, pH 5.5 and 30 °C. No enzyme leakage from the support was detected and hydrolysis yield of both 84 and 95% were attained with UF- and MF-membranes, respectively.